There are many applications that need optical scanners to convert objects, such as text and graphics objects on paper-based materials for example, to an electronic format that can be subsequently analyzed, distributed and archived. One of the most popular type of optical scanners is a flatbed scanner type device that converts objects, including pictures and papers, to image data that can be used, for example, for building Web pages and optical character recognition. The optical scanners are sometimes referred to as image scanners as the output thereof is generally in digital images.
FIG. 1 demonstrates a conventional flatbed scanner 100. Similar to a copy machine, flatbed scanner 100 includes a cover or lid 102 and a glass panel 103. Generally a scanning document 108 must be placed on glass panel 103 and faced down with lid 102 closed, so that an image sensing mechanism or imager in compartment 104 can properly scan scanning document 108.
Flatbed scanner 100 is suitable for many applications, however, the color accuracy of data generated by scanner 100 can be improved. One way to improve color accuracy is to increase the number of color channels. One way to do this has been disclosed in our co-pending U.S. patent application Ser. No. 11/263,482 entitled “Image Optimization System and Method” filed 31 Oct. 2005, the disclosure of which is incorporated herein by reference. Ser. No. 11/263,482 uses a monochrome CIS sensor and a plurality of narrow band LED sensors. This type of scanner is a vast improvement, but does not give the highest image quality possible.
LED's can be expensive and do not produce much light. Consequently scan speed tends to be slow. Hence it is advantageous to develop a higher quality scanner that is operable to provide improved color accuracy. Generally, this type of scanner uses multiple rows of filtered sensors that are usually red, green and blue. However, additional useful channels cannot be created by simply increasing the number of filtered rows of sensors as the spectral properties of the light source tend to limit color accuracy. The alternative, as disclosed in Ser. No. 11/263,482, is to use a second light source with different spectral properties. Then two scans can be used to provide the additional spectral information required to give improved color accuracy. Registration difficulties and noise amplification can cause problems when using two scans.